1. Field of the Invention
This invention relates to a waste disposal apparatus; and, more particularly, to an improved rotary impeller assembly in a waste disposal apparatus.
2. Description of the Prior Art
It is well known to provide food disposers with grinding lugs secured to a rotor and disposed to cooperate with a stationary grinding surface in the disposer for grinding and shredding waste materials and garbage. Efficient comminution of the materials is accomplished when the grinding lugs are rigidly and unyieldably secured to the rotor. Thus, it has been conventional to rigidly secure the lugs to the rotor and prevent any relative movement therebetween. Although disposers equipped with these stationary lugs achieve good grinding action, they redily become jammed when a substantially uncomminutable material, such as silverware, glass or the like, become lodged between the lug and the grinding surface. Each time such jamming occurs, the machine must be shut down until the hard material is dislodged.
The art then turned to the use of impellers which can either rotate 90.degree., 180.degree. or 360.degree.. In units wherein the impeller assembly rotates 90.degree. or 180.degree., the rotary impeller assembly is subject to impact or shock loading of the rotor and impeller as the impeller moves between retracted and extended positions. As the impeller engages bones or other objects of waste material resisting comminution only by absorbing the impact, it is possible to try to eliminate the objectionable vibration resulting from the impact and the noise resulting from vibration of the operating unit. While free yielding lugs or hammers sacrifice some of the grinding efficiency of the fixed lugs, shut-downs are virtually eliminated. The need has been seen for a comminuting assembly which achieves the advantages of both the fixed and swingable types without the disadvantages of either. That is, an impeller that has the grinding capability of a fixed lug, in conjunction with the ease of unjamming of the rotatable impellers when abnormally hard or oversize objects are encountered by the waste grinder.